Present oral therapy for relief of Parkinson's disease (PD) symptoms is inadequate. The purpose of this protocol is to examine the clinical responses of subjects with advanced PD to intravenous administration of pramipexole, a novel dopamine agonist. This study will define the initial clinical dose-response characteristics of i.v. pramipexole and compare them to i.v. L-DOPA, the "gold standard" for PD treatment. Results from this study will allow additional research into continuous i.v. treatment of PD symptoms. Recruitment is ongoing.